One-pot morphogen driven self-constructing films based on non-covalent host-guest interactions

The construction of films with complex architectures through one-pot reactions taking place exclusively on a surface remains a challenge. Recently, to address this problem, we introduced a concept based on morphogen-driven film buildup. We used Cu(I) as morphogen and the Huisgens click-reaction between azide and alkyne groups on polymers as film building blocks. Here, we extend this concept to films whose integrity is based exclusively on non-covalent host-guest interactions that are reversible allowing much broader tunability of the film properties. We trigger electrochemically the self-construction of films based on clickable host (cyclodextrin) and guests (ferrocene or adamantane) both functionalized by alkyne functions and poly(acrylic acid) bearing azide groups. Under voltammetry cycles, where Cu(I) is formed in situ from Cu(II), the film builds up by the non-reversible covalent grafting of the host and guest molecules to poly(acrylic acid) chains through triazole formation and by the subsequent formation of reversible host-guest interactions which entirely support the film cohesion. This process leads to the continuous self-construction of a nanometre size film whose thickness increases with the application time of the electrochemical stimulus. The growth rate of the film can be tuned by changing in the buildup solution either the relative ratio in concentration of host and guest or through the competition between clickable and non-clickable guest molecules. The effect of different stimuli leading to the dissolution of the film is also reported.